Window sill



FIG. 1 is a side elevational view showing my new design;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a perspective view thereof;

FIG. 5 is a front elevational view thereof; and,

FIG. 6 is a rear elevational view thereof. 

The ornamental design for a window sill, as shown. 